Jonathan Farwell’s late brother used to tease him about aging by saying, “Now you’re old enough to play Lear without the makeup.”

Well, not quite.

When OpenStage opens “King Lear” tonight with 79-year-old Farwell in the title role, it will require a slight suspension of disbelief. The doddering old ruler of ancient Britain is supposed to be 80, after all. So young Farwell is still a tad green for the role.

And yet, in all seriousness, Farwell must be one of the oldest actors to have ever taken on a part he calls “the hardest ever written, no matter how you look at it.”

It’s one far more commonly played by men decades Farwell’s junior — and for obvious reasons.

The journey of a man from blithe omnipotence to a fiery, senile madness that is ignited by his daughters’ betrayal and his own stupidity can take a physical and emotional toll on any actor. Then there’s the matter of committing a massive Shakespearean epic to a 79-year-old brain.

“I guess I’ve just been blessed genetically,” said Farwell. “I forget all kinds of things in my daily existence, but so far, the part of the hard drive that I use for memorizing lines is still functional.”

Last summer, John Hutton played Lear for the Colorado Shakespeare Festival at a spry 55. In 2007, the Denver Center Theatre Company’s Philip Pleasants tackled the job at 70.

At least at 79, Farwell says, “I don’t have to work technically at playing old. . . . I am old.

“I hope I bring some degree of authenticity to the role that you might not find in a younger man in heavy makeup.”

But if anything, Farwell says, “I probably have too much energy for my age. Sometimes, I feel myself being so energetic on stage, in fact, that I wonder if people might think I’m too young for the part.”

They might at Farwell’s gym. He’s been working out three times a week for months, and for a definite purpose. “I may be old, but I still have to be able to carry (daughter) Cordelia at the end,” he said.

Farwell’s lengthy stage resume includes four Broadway shows (he had the thankless job of understudying Yul Brynner in “The King & I”) and 11 years at regional theaters. He was the first El Gallo, back when “The Fantasticks” was a college workshop.

He moved to the Fort Collins area in 2005 with his wife, Deb Note-Farwell, who plays his Fool in a “Lear” that will be staged in the intimate confines of a Masonic Temple. And we do mean “his” Fool. Director Peter Anthony’s staging is set in an ancient mythological, mystical realm that combines Eastern and Western influences. And in this Druidic world, only Lear sees the Fool. “She’s my Jiminy Cricket,” Farwell said.

Anthony, who is known for playing fast and loose with a script, has pared what can be a marathon to a taut 2½ hours. That’s probably best for today’s faster-paced audiences — and it’s definitely best for Farwell.

“Peter keeps things relevant to the spinal action of the play, so it really moves,” Farwell said. “It’s enough of Lear that I feel like I am doing the role — but not so much that it’s killing me.”

(Editor’s note: The running time of the production on opening night was actually 3 hours.)

Lear is Farwell’s “bucket list” role. The closest he’s come in 60 years was a 2006 Fort Collins production of “The Dresser,” the backstage tale of a broken-down Shakespearean actor making his final performance as Lear.

“I’ve done Shakespeare all my life, and it would be a shame if I didn’t tackle Lear before it’s too late,” said Farwell, himself a father of two daughters. “This man has been this irascible, belligerent, tyrant king for so long that he knows no other way of living. And he is so unprepared for the reversal of fortune that happens to him because he can’t understand the difference between flattery and honesty. So he makes terrible mistakes in judgment, and it drives him nuts.

“But the sense of redemption at the end can only come to a man who has been through the mill of insanity, and come out the other end.”

While Lear might make the perfect swan song to any storied acting career, Farwell has no intention of slowing down. He’s already signed on for a play called “Trying” at the nearby Bas Bleu Theatre.

This weekend’s Best Bet

For the second straight summer, Stapleton MCA is presenting free, family-friendly musical theater at Founders Green, East 29th Avenue and Quebec Street. Like the 1984 Kevin Bacon film that inspired it, “Footloose, The Musical” follows the story of a boy who moves with his mother to a small town where dancing is prohibited by law. You’ll hear familiar songs from the movie (“The Girl Gets Around,” “Holding Out for a Hero,” “Let’s Hear It for the Boy,” “Almost Paradise” and the title tune) with original songs written for the stage adaptation. Showtimes 7 p.m. June 3-4 and June 10-11. 303-739-1970 or aurorafox.org.

This weekend’s other theater openings

“Hostage Song” In this intense, political rock musical, two terrified hostages find themselves bound and blindfolded in an unnamed country. As time passes, the man and woman dispel the tension through power-pop ballads and anthems of rage and longing. Through July 10. Bas Bleu Theatre, 401 Pine St., Fort Collins, 970-498-8949 or basbleu.org

“Nunsense”Can you believe those five zany nuns from Hoboken are still trying to raise money to bury their felled fellow sisters, done in by Sister Julia (Child of God)’s tainted soup? Through June 12. Presented by the Platte Valley Players at the Brighton Cultural Center, 300 Strong St., Brighton, 303-481-8432 or plattevalleyplayers.org

“The Pirates of Penzance” The Empire Lyric Players, organized in 1958 by Holy Family High School graduates, is committed to preserving Gilbert & Sullivan’s legacy by presenting one annual operetta. This one, from 1879, is about a young man’s exploits once he is released from his apprenticeship to a band of tenderhearted pirates. Through June 12. At the Mizel Center, 350 S. Dahlia St., 303-798-6700 or elps.org

The Running Lines blog

Video podcast: Coloradans on New York stages

All this month, we will be posting video podcasts with John Moore and Colorado actors gainfully working on New York stages, including Elizabeth Welch, Gene Gillette, Laura Tesman, Josh Franklin, Rachel de Benedet, Joshua Buscher, Jenny Fellner, Gavin Lodge, Alena Watters and Victoria Matlock. denverpost.com/theater.

Part 1: The introduction

Our series begins with this short video briefly introducing each Colorado actor we tracked down in New York City.

Part 2: Gene Gillette and Laura Tesman

Gene Gillette and Laura Tesman discuss “Bound,” an adaptation of the Prometheus and Pandora myths (and more), which they co-wrote. He stars, she directs. Running time: 5 minutes.